The present invention relates to an agricultural tillage apparatus; and more particularly, it relates to a tillage apparatus providing independent depth adjustment of two sets of ground working tools carried upon a main frame and sub-frame respectively.
Efficient farming requires a limited number of passes over the farm land in order to reduce man hours on the field and maximize the work done with a given amount of fuel. In order to combine various operations within one-pass over the field, differing types of ground working tools have been mounted on an implement for simultaneous use as the implement travels over the field. For example, two operations, cutting and burying trash, can be performed simultaneously by mounting coulter disks, which cut trash, to the front of an implement followed by chisel plows, which bury trash, mounted to the rear. Ideally, a farm implement would be able to accommodate the physical differences in size and shape between at least two sets of ground working tools and the differing operating demands of each set of tools as dictated by environmental factors. Independent depth control allows differing tools to be used simultaneously and effectively on the same implement.
My U.S. Pat. No. 4,245,706 for a One-Pass Complete Tillage System issued Jan. 20, 1981, discloses an adjustment mechanism for independently setting the depth of ground-working tools mounted on an implement frame. That adjustment mechanism includes two separate rock shafts, a forward one and and a rear one, each having its own bearings and journals to permit it to rotate a four-bar linkage which connects the sub-frame to the main frame for adjusting the sub-frame vertically relative to the main frame while maintaining the sub-frame parallel to the main frame. The-four bar linkage includes an actuator arm pivotally connected to the rod end of a hydraulic cylinder at one end. The other end of the actuator arm is attached to a first or forward rock shaft which is rotatably mounted to the main frame. Forward links are welded to each end of the forward rock shaft for rotation therewith with one end pivotally connected to a sub-frame. A parallel linkage, also controlled by the actuator arm and the forward rock shaft, extends rearwardly to operate a crank mounted to a second or rear rock shaft. Rear links affixed to the rear rock shaft mirror the movement to lift the rear of the sub-frame. A turnbuckle is incorporated in the parallel linkage to make minor adjustments in the operating depth of the front and rear sets of the disk blades carried on the sub-frame and to provide adjustment for wear.
The system disclosed in my earlier patent is capable of great vertical adjustment because the two rock shafts and connecting turnbuckle cooperate to eliminate problems of lock-up or jamming of the pivoting link mechanism by applying rotational forces symmetrically above and below the link means. Thus, that system includes a driven rock shaft which is capable of rotation of 150 or more. However, that system is also expensive to manufacture because of the cost involved in the second rock shaft and its associated bearings and journals.